Current sensing device and method for producing the same

ABSTRACT

Provided is a current sensing device including an electrical conductor made of electrically conductive metal; and voltage sensing terminals provided on the electrical conductor. Each voltage sensing terminal is formed by inserting bar-like metal into a through-hole formed in the electrical conductor, and the voltage sensing terminal includes a first terminal portion that is stored in the through-hole and a second terminal portion that protrudes from the through-hole.

TECHNICAL FIELD

The present invention relates to a current sensing device and a methodfor producing the same.

BACKGROUND ART

As a technique for detecting current of batteries of automobiles and thelike, a shunt-based current sensing method that uses a metal plateresistor is used. This method is also called four-terminal measurementand is a high-accuracy current sensing method.

Factors for sensing current with high accuracy include the types ofresistive materials used, the shapes and structures of resistors, andthe like. Further, the current sensing accuracy is also influenced bythe positional accuracy of voltage sensing terminals for sensingvoltage. In particular, when the resistance value is less than or equalto 1 mΩ, the current sensing accuracy is greatly influenced by thepositions of voltage sensing terminals.

Patent Literature 1 discloses a technique of forming voltage sensingterminals through stamping and formation of screws. In addition, PatentLiterature 2 discloses a technique of providing two plate-form basematerials integrally formed with a resistive element and disposingmeasuring terminal portions on the respective base materials.

CITATION LIST Patent Literature

Patent Literature 1: JP 2012-531760 A

Patent Literature 2: JP 2009-244065 A

SUMMARY OF INVENTION Technical Problem

Patent Literature 1 discloses a structure for sensing voltage by meansof fastening screws. However, there is a possibility the sensingaccuracy may be influenced by tightening torque or loosening.

In addition, Patent Literature 2 discloses a technique of weldingmeasuring terminal portions to the surfaces of base materials 12 a, 12b, respectively, but it is difficult to maintain the positionalaccuracy. In addition, when such a structure obtained by joiningmeasuring terminals and base materials together at their surfaces isused, high-accuracy sensing is difficult to perform unless the surfacesare joined uniformly, which is problematic.

It is an object of the present invention to maintain the positionalaccuracy high when voltage sensing terminals are formed.

Solution to Problem

According to an aspect of the present invention, there is provided acurrent sensing device including an electrical conductor made ofelectrically conductive metal; and voltage sensing terminals provided onthe electrical conductor. Each voltage sensing terminal is formed byinserting bar-like metal into a through-hole formed in the electricalconductor, and the voltage sensing terminal includes a first terminalportion that is stored in the through-hole and a second terminal portionthat protrudes beyond the through-hole.

Since the first terminal portion is stored in the through-hole, thecurrent sensing terminal fits stably.

The voltage sensing terminal preferably includes a flange portion, andthe flange portion preferably abuts the electrical conductor. The flangeportion preferably includes two flange portions adapted to sandwich theelectrical conductor therebetween. With the flange portion(s), thevoltage sensing terminals are fixed firmly. At least an opening on oneside of the through-hole preferably forms a recess portion with anincreased inside diameter. The electrical conductor includes a resistiveelement and electrode terminals joined to the resistive element, and thevoltage sensing terminals are provided on the respective electrodeterminals.

The electrical conductor may include narrow portions, and the narrowportions may be provided between the voltage sensing terminals.

According to another aspect of the present invention, there is provideda method for producing a current sensing device, including preparing anelectrical conductor; machining a part of the electrical conductor so asto form narrow portions and machining the electrical conductor so as toform a pair of through-holes in the respective narrow portions, anddisposing voltage sensing terminals in an upright position in therespective through-holes.

Since machining of the electrical conductor in the width direction andmachining of the electrical conductor to form through-holes therein areperformed in the same step, and voltage sensing terminals are disposedin an upright position in the respective through-holes, the positionalaccuracy when the voltage sensing terminals are formed can be maintainedhigh.

The present specification incorporates the disclosure of JP PatentApplication No. 2015-124619 that forms the basis of the priority claimof the present application.

Advantageous Effects of Invention

According to the present invention, the positional accuracy when voltagesensing terminals are formed can be maintained high.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an exemplary configuration of acurrent sensing device that uses a resistor in accordance with anembodiment of the present invention.

FIGS. 2A and 2B are views showing a method for producing a currentsensing device that uses a resistor in accordance with a secondembodiment of the present invention, and showing a plan view and across-sectional view in pairs.

FIGS. 3C and 3D are views continued from FIGS. 2A and 2B.

FIGS. 4E through 4G are views continued from FIGS. 3C and 3D.

FIG. 5 is a view showing the positional relationship between a joinedportion of a resistive element and an electrode terminal and athrough-hole.

FIG. 6A shows a view in which the resistance value of a completedresistor is measured using a four-terminal measurement method. FIG. 6Bshows a view in which a display portion, which has been obtained byencoding data such as a measured resistance value into a QR code or thelike, is written onto the surface of an electrode of a current sensingdevice.

FIG. 7 is a view showing an exemplary circuit configuration of a currentsensing module.

FIG. 8A is a view showing an exemplary configuration of the externalappearance of a current sensing module. FIG. 8B is a cross-sectionalview showing an exemplary configuration of the current sensing module.FIG. 8C is a plan view showing an exemplary configuration of the currentsensing module.

FIG. 9 is a flowchart showing an exemplary process flow in accordancewith a third embodiment.

FIGS. 10A through 10C are views showing a method for producing aresistor in accordance with a fourth embodiment of the presentinvention, and showing a plan view and a cross-sectional view in pairs.

FIGS. 11D through 11F are views continued from FIGS. 10A through 10C.

FIGS. 12A and 12B are views showing a method for producing a resistor inaccordance with a fifth embodiment of the present invention, and showinga plan view and a cross-sectional view in pairs.

FIGS. 13C through 13E are views continued from FIGS. 12A and 12B.

FIGS. 14A through 14D are views showing a method for producing aresistor in accordance with a sixth embodiment of the present invention,and showing a plan view and a cross-sectional view in pairs.

FIGS. 15A and 15B are views showing examples of terminal structures.

FIGS. 16A and 16B are views showing examples of terminal structures.

FIGS. 17A through 17C are views showing an example of a terminalstructure.

FIG. 18 is a view showing an example of a terminal structure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a current sensing device in accordance with an embodimentof the present invention will be described in detail with reference tothe drawings.

In this specification, “welding” refers to a joining method thatincludes applying heat, pressure, or both to joined portions of two ormore members and also adding proper filler metal thereto as appropriateso as to form a single member of the integrated, continuous joinedportions.

Hereinafter, a current sensing device in accordance with an embodimentof the present invention will be described in detail with reference toan example of a current sensing device that uses a resistor with abutt-joint structure in which end faces of a resistive element and endfaces of electrodes are butt-joined together, respectively. It should benoted that such a technique can also be applied to a structure in whicha resistive element and electrodes are connected together at theirsurfaces.

In this specification, a direction in which an electrode, a resistiveelement, and another electrode of a resistor are arranged is referred toas a length direction, and a direction that intersects the lengthdirection is referred to as a width direction.

First Embodiment

First, a current sensing device that uses a resistor in accordance witha first embodiment of the present invention will be described. FIG. 1 isa perspective view showing an exemplary configuration of a currentsensing device that uses a resistor in accordance with this embodiment.A current sensing device 1 that uses a shunt resistor (hereinafterreferred to as a “resistor”) shown in FIG. 1 includes two electrodes 5 a(first electrode), 5 b (second electrode), a resistive element 3disposed between the electrodes 5 a, 5 b, and voltage sensing terminals17. It should be noted that a portion including the resistive element 3and the electrodes 5 a, 5 b is also referred to as an electricalconductor. In addition, the electrodes 5 a, 5 b are also referred to aselectrode terminals. The electrodes 5 a, 5 b include end-side mainelectrode portions (herein, portions excluding 5 c, 5 d of theelectrodes 5 a, 5 b are defined as main electrode portions) and narrowelectrode portions 5 c, 5 d that are located on the side of theresistive element 3 and have widths narrower than those of the mainelectrode portions by 2W₂, respectively. The resistive element 3 isdisposed between the narrow electrode portions 5 c, 5 d. It is assumedthat the dimension of each of the narrow electrode portions 5 c, 5 d inthe length direction is W₁. The dimension W₁ herein is about 1 to 3 mm,for example.

In this example, a single voltage sensing terminal 17 is provided oneach of the narrow electrode portions 5 c, 5 d. When the voltage sensingterminals 17 are provided on the narrow electrode portions 5 c, 5 d,respectively, the distance between the voltage sensing terminals 17 canbe shortened, and thus the current measurement accuracy in four-terminalmeasurement can be improved.

In the structure shown in FIG. 1, recess portions 7 are provided thatare recessed inward in the width direction of a part of a regionincluding the joined portions 13 a, 13 b, which have been formed bywelding the resistive element 3 and the electrode portions 5 a, 5 btogether, for example, so that narrow portions with narrow widths can beformed. In such a case, the width of each of the narrow electrodeportions 5 c, 5 d is substantially equal to that of the resistiveelement 3. Portions that are formed by the recess portions 7 and thusare narrow are referred to as narrow portions (hereinafter the same).

According to the resistor in this embodiment, since the recess portions7 are formed in a part of a region including the joined portions 13 a,13 b of the resistive element 3 and the electrode portions 5 a, 5 b, itis possible to suppress concentration of stress generated across theshunt resistor on the joined portions 13 a, 13 b of the current sensingdevice 1.

Even when the recess portions 7 are formed to a length of about 1 to 3mm (W₁) from the boundaries between the resistive element 3 and theelectrodes 5 a, 5 b, a stress relaxation effect of greater than or equalto 10% is obtained. Further, providing the recess portions 7 canstabilize current distribution in a current path, and thus can improvethe TCR characteristics.

It should be noted that in FIG. 1, reference numeral 15 denotes boltholes. Reference numeral 11 denotes holes for fixing a current sensingsubstrate (which will be omitted hereinafter). In addition, referencenumeral 17 denotes voltage sensing terminals that are provided on thenarrow electrode portions 5 c, 5 d, respectively, in this example. Whenthe voltage sensing terminals 17 are provided on the narrow electrodeportions 5 c, 5 d, respectively, the distance between the voltagesensing terminals 17 can be shortened, and thus the current measurementaccuracy in four-terminal measurement can be improved.

In addition, a code display portion 12 in which a code is displayed isformed on the upper face of the first electrode portion 5 a, forexample. The display of the code will be described later.

Second Embodiment

Next, a method for producing a current sensing device that uses aresistor in accordance with a second embodiment of the present inventionwill be described. As an example of a current sensing device that uses aresistor to be produced, the structure shown in FIG. 1 is used.

FIGS. 2 to 4 are views each showing a method for producing a currentsensing device that uses a resistor in accordance with this embodiment,and showing a plan view and a cross-sectional view in pairs.

As shown in FIG. 2A, first, an electrode material 31 with highelectrical conductivity, such as Cu, is prepared.

As shown in FIG. 2B, the bolt holes 15 for screwing and a hole portion33 adapted to have a resistive material embedded therein are formed inthe electrode material 31 using a method such as pressing, cutting, orlaser machining. Specifically, a single hole portion 33 is provided at asubstantially central position of the electrode material 31, and a pairof bolt holes 15 are provided at positions close to the ends of theelectrode material 31 in the length direction.

As shown in FIG. 3C, a resistive material 35 prepared in advance, whichhas substantially the same size as the hole portion 33 and has higherresistance than the electrode material 31, is embedded in the holeportion 33. Therefore, the outer side face of the resistive material 35abuts the inner side face of the hole portion 33 so that joined portionsin a rectangular shape are formed, for example.

For both the electrode material 31 and the resistive material 35, longmaterials (plates) that have been cut out can be used, for example.

As the resistive material 35, a metal plate material such as a Cu—Ni,Cu—Mn, or Ni—Cr-based material can be used.

As shown in FIG. 3D, the resistive material 35 is fixed in the electrodematerial 31 using a pressing jig 41 or the like, and is scanned with anelectron beam or a laser beam 43, for example, as indicated by referencenumeral L1 so that the joined portions of the electrode material 31 andthe resistive material 35 are welded together and a joined base materialcan thus be formed that has the electrode material 31 and the resistivematerial 35 embedded in and joined to the central region of theelectrode material 31.

Since the through-hole (hole portion 33) is provided in the electrodematerial 31, and the resistive material 35 is embedded in thethrough-hole, distortion of the electrode material 31 (workpiece) can besuppressed even when welding is performed with an electron beam or thelike. Further, when the pressing jig 41 is used, distortion of theworkpiece can be suppressed more, which is advantageous.

As shown in FIG. 4E, in order to determine the resistance value, pressworking (45) for determining the width of the resistive material 35 isperformed, for example. Herein, regions including the ends of theresistive material 35 in the width direction are cut off to form therecess portions 7 (FIG. 4F). Then, as the resistive material 35 embeddedis partially cut off from side faces thereof with respect to the initialwidth, the width of the resistive element becomes smaller and theresistance value can thus be adjusted. Further, if the start point andthe end point of welding are cut off, variations in joining of thejoined portions 13 a, 13 b can also be suppressed and stress can thus berelaxed.

Further, through-holes 36 adapted to have voltage sensing terminalsprovided therein are also formed in this step. Therefore, since thepositional relationship of the voltage sensing terminals is stabilized,and since the step of adjusting the resistance value and the step ofpositioning the voltage sensing terminals are performed in the samestep, high-accuracy current sensing with small variations in therelationship with the resistance value is possible.

As shown in FIG. 4G, voltage sensing terminals 17 are formed. Forexample, bar-like terminals are inserted into and disposed in an uprightposition in the through-holes 36 of the narrow electrode portions 5 c, 5d.

Through the aforementioned production steps, a current sensing devicethat uses the resistor shown in FIG. 1 can be produced.

It should be noted that as the material of the voltage sensing terminals17, copper, brass, phosphor bronze, or copper alloy such as Corson alloyis preferably used.

It should be noted that when electron beam welding or the like isperformed as shown in FIG. 3D, there is a possibility that the joinedstate at the start point and the end point of the joined portion maybecome unstable and such portion can become the origin of breakage.Herein, if cutting is performed at a portion including the start pointand the end point as shown in FIG. 4E, it is possible to maintain theexcellent joined state in addition to obtaining the aforementionedstress relaxation effect.

In addition, as shown in FIG. 5, the through-holes 36 are formed to havea positional relationship with the joined portions 13 a, 13 b of theresistive element 3 and the electrode terminals 5 c, 5 d such that thethrough-holes 36 are away from the joined portions 13 a, 13 b by W₁₁.That is, since the joined portions 13 a, 13 b have been alloyed throughelectron beam welding or the like, the joined portions 13 a, 13 b aredifficult to be machined for forming the through-holes 36. Therefore, ifthrough-holes are formed in regions excluding the alloyed regions, thethrough-holes 36 can be formed with high accuracy.

As described above, the production method in this embodiment isadvantageous in that the positional accuracy of the voltage sensingterminals in the current sensing device can be maintained high.

Third Embodiment

Next, a current sensing device with a code display portion in accordancewith a third embodiment of the present invention will be described. Thecode display portion 12 shown in FIG. 1 contains the following data, forexample. That is, the code contains data such as a lot number, productname, value indicating characteristics (e.g., resistance value and TCRvalue), materials used (e.g., resistive material), producer, productionsite, production date, and user information (e.g., company that providesthe product). In particular, if a code of data such as a combination ofa lot number and a resistance value or data obtained by adding a TCRvalue thereto is displayed on a resistor after the resistor is produced,a user is able to know correct data and the like without actuallymeasuring the resistance value, for example, which is very convenient.The value indicating characteristics is preferably the actually measuredvalue, but may also be the design value. For example, the actuallymeasured value may be recorded for the resistance value and the designvalue may be recorded for the TCR value.

FIGS. 6 to 9 are views for illustrating a current sensing device with acode display portion in accordance with this embodiment and a productionmethod therefor.

As shown in FIG. 9, a process is started (step S1: Start), and in stepS2, a current sensing device that uses a resistor is produced asdescribed in the first and second embodiments (see FIG. 1).

Next, in step S3, the resistance value and the like of the resistor aremeasured. FIG. 6A is a view in which the resistance value of thecompleted resistor is measured with a four-terminal measurement method.The resistance value of the resistor is actually measured with afour-terminal measurement method using the voltage sensing terminals 17,17 and the electrodes 5 a, 5 b. Besides, data that is necessary (e.g.,TCR value) may also be measured.

Next, in step S4, as shown in FIG. 6B, the display portion 12, which hasbeen obtained by encoding data such as the measured resistance valueinto a QR code or the like, is written onto the surface of the electrode5 a of the current sensing device, for example. That is, informationsuch as a characteristic value is encoded and printed onto theelectrode.

For the printing method herein, fiber laser, semiconductor laser, greenlaser, electron beam, Yag laser, printing (inkjet printing), or the likecan be used. In addition, as a print pattern, a QR code (registeredtrademark), data matrix, barcode, a two-dimensional code, or the likecan be used.

The print place (position) is preferably the copper electrode portion 5a or 5 b. It should be noted that printing on the resistive element 3 ispreferably avoided considering the influence on the characteristics ofthe resistor.

Examples of printing on the copper electrode include a method of shavinga part of the surface through laser marking or coloring a part of thesurface in black through carbonization.

A user or the like who is provided with the current sensing device thatuses the resistor reads data on the QR code using a smartphone or adedicated decoding device, for example (step S11) so that the processterminates.

With the aforementioned technique, a user or the like of the resistor isable to manage and check the resistance value only by reading a code ofthe display portion 12 through a code reader or the like and without theneed to possess a system for measuring the resistance value. Therefore,traceability based on digital data is possible. Problems such aserroneous mounting can also be avoided.

Next, an exemplary configuration of the current sensing module will bedescribed. FIG. 7 is a view showing an exemplary circuit configurationof the current sensing module. FIG. 8A is a view showing an exemplaryconfiguration of the external appearance of the current sensing module.FIG. 8B is a cross-sectional view showing an exemplary configuration ofthe current sensing module. FIG. 8C is a plan view showing an exemplaryconfiguration of the current sensing module.

The current sensing module A shown in FIG. 7 includes the aforementionedresistor 1, an amplifier 63 that amplifies a voltage signal across theopposite terminals of the resistor 1, an A/D converter 65 that A/Dconverts a signal amplified by the amplifier 63, and a microcomputer 67that performs computation upon receiving a digital signal output.

When current flows through the current sensing device 1, a voltage levelacquired by the voltage sensing terminals 17 of the current sensingdevice 1 is amplified and converted into digital data so that a currentvalue is computed by the microcomputer 67. The current value is sent toa variety of electrical appliances via a data bus and the like.

As the circuit shown in FIG. 7, a variety of elements are mounted on adetection circuit portion 101 as shown in FIGS. 8A to 8C and areconnected to the current sensing device so that the module is formed.The detection circuit portion 101 is sheathed through molding asappropriate. The code display portion 12 is preferably disposed at aposition where it is not shielded by the detection circuit portion 101or the mold. As shown in FIG. 8B, a PCB 105 is mounted on the currentsensing device 1 and is molded or encapsulated in a case as appropriateso that the current sensing module A is formed. The voltage sensingterminals 17 penetrate to the front surface side from the rear surfaceside of the PCB 105. The PCB 105 and the current sensing device 1 arescrewed via the through-holes indicated by reference numeral 11 inFIG. 1. The PCB 105 is preferably formed of a thermally conductive,electrically insulating material so that heat generated from theresistor is detected. The PCB 105 has a semiconductor chip 111 and thelike mounted thereon.

FIG. 8C is a plan view of the portion of the PCB 105. The voltagesensing terminals 17 exposed on the front surface side of the PCB 105are solder-connected to contacts 109 formed on the PCB 105. The contacts109 and the semiconductor chip 111 are connected together by wires 107.The semiconductor chip 111 incorporates the aforementioned amplifier,A/D converter, and microcomputer. The semiconductor chip 111 connectswith a connector 141 so that a current value can be output.

To incorporate such a current sensing device 1 in the current sensingmodule A, the code display portion 12 of the current sensing device 1 isread so that specific information such as the resistance value and TCRvalue is recorded on ROM in the microcomputer 67. Since a CPU in themicrocomputer 67 computes the current value using such information,higher-accuracy current detection is possible. In addition, it is alsopossible to measure the temperature of or around the current sensingdevice 1 using a temperature sensor (not shown) and compute the currentvalue by using the TCR value and applying necessary correction thereto.

Fourth Embodiment

Next, a method for producing a current sensing device that uses aresistor in accordance with a fourth embodiment of the present inventionwill be described. As an example of a current sensing device that uses aresistor to be produced, the structure shown in FIG. 1 is used.

FIGS. 10 and 11 are views each showing a method for producing a resistorin accordance with this embodiment, and showing a plan view and across-sectional view in pairs.

As shown in FIG. 10A, for example, a resistive material 53 in a longflat-plate shape or the like, and first and second electrode materials51, each of which is made of an electrode material with higherelectrical conductivity than that of the resistive material 53 and is ina long flat-plate shape like the resistive material 53, are prepared.

As shown in FIG. 10B, opposite end faces of the resistive material 53and end faces of the first and second electrode materials 51 arearranged such that they contact each other and from joined portions.Then, the joined portions 55 are welded together with an electron beamor a laser beam 57, for example, as indicated by reference numeral L1 sothat a single flat plate is formed. Various adjustments such asadjustments of the resistance value and shape can also be performedthrough adjustment of the joined positions.

As shown in FIG. 10C, a plurality of through-holes 36 are formed in thefirst and second electrode materials 51 around the joined portions 55along the joined portions 55.

As shown in FIG. 11D, the resistor material (joined base material)including the joined portions 55 is cut using a die 59 that extends inthe length direction and is wider in a region including the resistivematerial 53 and the electrode materials 51 around the resistive material53. As shown in FIG. 11E, the joined portions after the cutting areindicated by reference numerals 13 a, 13 b.

As shown in FIG. 11E, a resistor that has recess portions 7 as in thefirst embodiment and has through-holes 36 in the narrow electrodeportions 5 c, 5 d can be formed. Next, as shown in FIG. 11F, bar-likemetal is inserted in the through-holes 36 so that voltage sensingterminals 17 are formed.

Through the aforementioned steps, a number of current sensing deviceseach having the main electrode portions 5 a, 5 b and the narrowelectrode portions 5 c, 5 d as well as the voltage sensing terminals 17can be produced.

It should be noted that the bolt holes 15, the holes 11 for fixing acurrent sensing substrate, and the like shown in FIG. 1 are omittedherein, but such holes may be either provided or not (which will also beomitted in the following description).

Fifth Embodiment

Next, a method for producing a current sensing device that uses aresistor in accordance with a fifth embodiment of the present inventionwill be described. As an example of a current sensing device that uses aresistor to be produced, the structure shown in FIG. 1 is used.

FIGS. 12 and 13 are views showing a method for producing a resistor inaccordance with this embodiment, and showing a plan view and across-sectional view in pairs.

The steps of forming the resistive material (joined base material) shownin FIGS. 12A and 12B are similar to those shown in FIGS. 10A and B.

As shown in FIG. 13C, the joined base material is stamped using a die 61with a shape as indicated by the dashed line, that is, a shape thatconforms to the shape of a resistor having recess portions in the lengthdirection. In the stamping step, a plurality of through-holes 36 areformed in the first and second electrode materials 51 around the joinedportions 53 along the joined portions 53. In such a case, a number ofresistors may be stamped out in a single step.

As shown in FIG. 13D, a resistor having the recess portions 7 in aregion including the joined portions 13 a, 13 b of the split member canbe formed. Therefore, advantageous effects similar to those in the firstto third embodiments can be obtained.

As shown in FIG. 13E, voltage sensing terminals 17 are formed on thenarrow electrode portions 5 c, 5 d, respectively.

Through the aforementioned steps, a number of resistors such as the oneshown in FIG. 1 that includes main electrode portions and narrowelectrode portions can be produced.

According to this embodiment, the step of determining the width of aresistive element and the step of forming through-holes in which voltagesensing terminals are adapted to be disposed in an upright position canbe performed concurrently. Therefore, advantageous effects are obtainedin that the steps can be simplified and the positioning accuracy isimproved.

Sixth Embodiment

Next, a method for producing a current sensing device that uses aresistor in accordance with a sixth embodiment of the present inventionwill be described. As an example of a current sensing device that uses aresistor to be produced, the structure shown in FIG. 1 is used. However,the joined portions of the electrodes and the resistive element are notformed herein.

FIG. 14 are views showing a method for producing a resistor inaccordance with this embodiment, and showing a plan view and across-sectional view in pairs.

As shown in FIG. 14A, a resistive material 71 is prepared. The resistivematerial 71 is a single metal plate material, such as Cu, for example.It should be noted that the resistive material 71 is also referred to asan electrical conductor.

As shown in FIG. 14B, the resistive material 71 is stamped using a die75 with a shape as indicated by the dashed line, that is, a shape thatconforms to the shape of a resistor having recess portions in the lengthdirection. During the stamping step, a plurality of through-holes 36 arealso formed in the resistive material 71. In such a case, a number ofresistors may also be stamped out through a single step.

As shown in FIG. 14C, a resistor with the recess portions 7 and thethrough-holes 36 is formed.

As shown in FIG. 14D, voltage sensing terminals 17 are formed in thethrough-holes 36, 36, which are formed in the region having the recessportions 7 formed thereon, respectively.

Through the aforementioned steps, a number of current sensing elementsthat use resistors can be produced using only a resistive material.

According to this embodiment, the step of determining the width of aresistive element and the step of forming through-holes in which voltagesensing terminals are adapted to be disposed in an upright position canbe performed concurrently. Therefore, advantageous effects are obtainedin that the steps can be simplified and the positioning accuracy isimproved.

Seventh Embodiment

Next, a seventh embodiment of the present invention will be described.In this embodiment, a terminal structure for providing voltage sensingterminals in an upright position on a resistor and a production methodtherefor will be described.

(1) Terminal Structure 1

FIG. 15A is a cross-sectional view showing an exemplary configuration ofthe terminal structure. In the structure shown in FIG. 15A, the voltagesensing terminal 17 is provided in the through-hole 36 formed in theelectrode 5 b (5 d). In the structure, a flange 81 is formed at anintermediate portion of the voltage sensing terminal 17. When thevoltage sensing terminal 17 is inserted in the through-hole 36, theinsertion position of the voltage sensing terminal 17 is determined bythe flange 81, and the inserted structure is also stabilized. Thevoltage sensing terminal 17 has a first terminal portion 17 b that isstored in the through-hole 36 and a second terminal portion 17 a thatprotrudes beyond the through-hole 36.

It should be noted that the voltage sensing terminal 17 is preferablypressed into the through-hole 36 but may also be welded to thethrough-hole 36.

(2) Terminal Structure 2

FIG. 15B is a cross-sectional view showing an exemplary configuration ofa terminal structure 2. In the structure shown in FIG. 15B, the voltagesensing terminal 17 is provided in the through-hole 36 formed in theelectrode 5 b (5 d). In the structure, a flange 83 is formed at one endof the voltage sensing terminal 17. When the voltage sensing terminal 17is inserted into the through-hole 36 from the lower side of the drawing,the insertion position of the voltage sensing terminal 17 is determinedby the flange 83, and the inserted structure is also stabilized. Thevoltage sensing terminal 17 includes a first terminal portion 17 b thatis stored in the through-hole 36 and a second terminal portion 17 a thatprotrudes beyond the through-hole 36. This is the same hereinafter.

It should be noted that the voltage sensing terminal 17 is preferablypressed into the through-hole 36 but may also be welded to thethrough-hole 36.

(3) Terminal Structure 3

FIG. 16A is a cross-sectional view showing an exemplary configuration ofa terminal structure 3. The structure shown in FIG. 16A is similar tothe terminal structure 1, but is a structure whose side inserted throughthe through-hole 36 has a protruding portion 85 that protrudes to therear side.

(4) Terminal Structure 4

FIG. 16B is a cross-sectional view showing an exemplary configuration ofa terminal structure 4. In the structure shown in FIG. 16B, theprotruding portion 85, which is a side of the terminal structure 3inserted through the through-hole 36 and protruding to the rear side, isbent to form a bent portion 87 that abuts the rear surface of theelectrode 5 b, so that the structure is fixed on the rear surface of theelectrode 5 b. Further, the bent portion 87 may be welded to the rearsurface of the electrode 5 b.

(5) Terminal Structure 5

FIG. 17 are views showing an exemplary configuration of a terminalstructure 5 and a production method therefor. As shown in FIG. 17A, aflange 95 is provided at an intermediate portion of the voltage sensingterminal 17, and a portion below the flange 95 is formed thicker than aportion above the flange 95 (terminal side). Meanwhile, the through-hole(36) formed in the narrow electrode portion 5 d on the electrode 5 bside is formed such that the diameter of a lower portion is larger thanthat of an upper portion. That is, the through-hole 36 is formed suchthat an upper through-hole 91 communicates with a lower through-hole 93(a recess portion with an increased inner diameter) so that a recessportion at an opening of the through-hole 36 is formed.

As shown in FIG. 17B, when the voltage sensing terminal 17 is insertedinto the through-hole 36 from above, the lower surface of the flange 95abuts the surface of the electrode 5 b (5 d).

As shown in FIG. 17C, a portion AR1 below the flange 95 is squashed sothat the portion AR1 below the flange 95 deforms to fit within the lowerthrough-hole 93, thereby filling the space with a large diameter so asto form a flange 97.

According to such a structure, the flange 95 and the flange 97 preventthe voltage sensing terminal 17 from being easily disengaged from thecurrent sensing device 1, and thus allow the voltage sensing terminal 17to be more firmly fixed on the current sensing device 1.

In addition, as shown in FIG. 17C, this structure is convenient sincethe flange 95 can be used as a spacer (with a thickness of t₂₁) when thePCB 101 is mounted on the current sensing device 1.

(6) Terminal Structure 6

FIG. 18 is a view showing an exemplary configuration of a terminalstructure 6. The structure shown in FIG. 18 is obtained by formingrecess portions at upper and lower openings of a through-hole. Such astructure can be formed by, in the structure shown in FIG. 17, fittingthe voltage sensing terminal into the upper recess portion and hammeringthe voltage sensing terminal into the lower recess portion. According tosuch a structure, an upper flange 99 and a lower flange 97 becomeapproximately flush with the upper and lower surfaces of the electrode 5b (5 d), respectively. Therefore, there is an advantage in that theprotrusions and recesses do not interrupt.

In the aforementioned embodiments, the configurations and the like shownin the attached drawings are not limited thereto and can be changed asappropriate within the range that the advantageous effects of thepresent invention are exerted. Further, the configurations and the likecan be changed as appropriate within the scope of the object of thepresent invention.

The configurations of the present invention can be freely selected, andan invention that includes the selected configurations is also includedin the present invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to current sensing devices.

REFERENCE SIGNS LIST

-   -   1 Current sensing device (Resistor)    -   3 Resistive element    -   5 a First electrode    -   5 b Second electrode    -   5 c, 5 d Narrow electrode portions    -   7 Recess portion    -   12 Code display portion    -   13 a, 13 b Joined portions    -   17 Voltage sensing terminal

All publications, patents, and patent applications that are cited inthis specification are all incorporated by reference into thisspecification.

What is claimed is:
 1. A current sensing device comprising: anelectrical conductor made of electrically conductive metal; and voltagesensing terminals provided on the electrical conductor, wherein: eachvoltage sensing terminal is formed by inserting bar-like metal into athrough-hole formed in the electrical conductor, and the voltage sensingterminal includes a first terminal portion that is stored in thethrough-hole and a second terminal portion that protrudes beyond thethrough-hole.
 2. The current sensing device according to claim 1,wherein: the voltage sensing terminal includes a flange portion, and theflange portion abuts the electrical conductor.
 3. The current sensingdevice according to claim 2, wherein the flange portion includes twoflange portions adapted to sandwich the electrical conductortherebetween.
 4. The current sensing device according to claim 1,wherein at least an opening on one side of the through-hole forms arecess portion with an increased inner diameter.
 5. The current sensingdevice according to claim 1, wherein: the electrical conductor includesa resistive element and electrode terminals joined to the resistiveelement, and the voltage sensing terminals are provided on therespective electrode terminals.
 6. The current sensing device accordingto claim 1, wherein: the electrical conductor includes narrow portions,and the narrow portions are located between the voltage sensingterminals.
 7. A method for producing a current sensing device,comprising: preparing an electrical conductor; machining a part of theelectrical conductor so as to form narrow portions, and machining theelectrical conductor so as to form a pair of through-holes in therespective narrow portions, and disposing voltage sensing terminals inan upright position in the respective through-holes.